Track mounted aerial lift platform apparatus

ABSTRACT

An aerial lift platform apparatus having tracks. A rotatable upper works is mounted on a chassis, and includes a turntable, a telescopic boom having a workman&#39;s platform at its outer end, and an engine driving a hydraulic pump. The chassis has forward and rear drive wheels on each side, and two pairs of intermediate idler wheels. Each pair of idler wheels is supported by a spring biased cranked axle which is journalled in bearings, to effect joint movement of the two wheels of the pair. All wheels have pneumatic tires and a track encompasses the tires on each side.

BACKGROUND OF THE INVENTION

The present invention relates to aerial lift platform apparatus, andmore particularly to such apparatus which is mounted on a chassis havingendless tracks or treads which engage the ground.

Aerial lift platform apparatus have been provided in the past, and theiruse has recently been significantly increasing. Such apparatus is in theform of a self-propelled vehicle having a chassis which is mounted onground engaging wheels. Smaller units often have three wheels, whilelarger units, having a vertical reach of between approximately fortyfeet and one hundred and twenty-five feet, are mounted on four wheels.The chassis supports a rotatable upper works, which is capable ofrotating through 360 degrees. A boom is carried by the upper works,having at or adjacent its outer end a workman's platform, usuallyprovided with upstanding walls so as to form a basket-like structure,for purposes of safety. The boom is often extensible, and is caused torotate through 360 degrees, due to its mounting on the upper works. Inaddition, the boom may be raised and lowered about a horizontal pivot.The upper works usually contains a prime mover, such as an internalcombustion engine, which drives one or more pumps, to thereby deliverpower to rotary motors positioned at one or more of the wheels in orderto propel the vehicle, and also to deliver hydraulic fluid underpressure to various cylinders, such as for steering and boom extensionand retraction. Rotation of the upper works is also effected by ahydraulic motor driven by the pump. All controls are provided induplicate, so that there is a set of controls accessible to a personstanding by the machine, and also a set of controls is provided at theplatform, so as to be accessible to the operator or workman in theplatform.

An aerial lift platform has been provided, mounted on a tracked vehiclechassis, instead of wheels. There was thereby gained the advantage ofpermitting operation where the supporting surface was relatively soft,and could not sustain a vehicle of such weight when mounted on wheels.This construction was a known crawler type construction which provided asteel driving sprocket and a steel idler at the ends, and intermediatesteel rollers which were rigidly mounted to the chassis. Thisconstruction, while suitable for use in terrain of a relatively softnature, provided no shock absorbing or cushioning for the operator, whocould only drive the vehicle from the the operator's platform.

In another embodiment, an aerial lift platform was provided which wasmounted on tracks, and was provided with a cab on the vehicle, which cabhad controls for moving the vehicle. The operator's platform was notprovided with controls for moving the vehicle, so that the operator,when the vehicle was moving, could only be in the cab which was mounteddirectly on the vehicle. Once the aerial lift platform was set inposition, an operator occupied the platform, and by manipulation of thecontrols in the platform on the boom, was able to rotate the upperworks, raise and lower the boom and extend and retract the boom, butcould not, as noted, cause the vehicle to move. In this construction,pneumatic tires were provided, for both drive and intermediate or idlerwheels, and the idler wheels were mounted on independent spring loadedaxles. That is, one or more of the idlers on one side of the chassiscould be moved upwardly, or downwardly, relative to a reference point onthe chassis, without causing movement of any idler on the opposite side,relative to the same or a corresponding reference point on the chassis.

The aerial lift platform apparatus having rigid suspension also had acab on the chassis, and thus required two operator's stations, one atthe cab and one at the platform, and there was thereby required extracost; in addition there was the problem that the vehicle could not bemoved by the operator in the cab and thus was more expensive from thepoint of view of personnel cost, and was somewhat less efficient. On theother hand, where the shock absorbing or cushioning type suspension wasutilized, including pneumatic tires and spring loaded intermediatewheels, stability was not as great as desired, particularly when theboom was extended over one side. It has been found that with the boomextended over one side, there is produced an over-turning moment tendingto tilt the machine and overturn it to the side over which the boomextends. The problem is known to be more severe where there is a shockabsorbing or cushioning or so-called "sprung" chassis, and this has beensolved in the past, for instance in connection with truck mountedcranes, by the use of outriggers. Thus, the truck mounted cranes havethe outriggers in stored, non-use position during movement of the truckmounted cranes from one place to another, but when relatively heavyloads are to be lifted, the outriggers are utilized, and theirpositioning in effect renders the spring mounting of the chassis on theground engaging wheels inoperative. That is, during the lifting of loadsnear the capacity of the truck mounted crane, the spring suspension ofthe chassis is made inoperative and the supporting of the chassis is bythe outriggers, which bypass the spring suspension of the chassis. Ofcourse, with such cranes, it is not possible to move them when theoutriggers are positioned.

There are known, also, mobile cranes which are intended to lift and movea load by movement of the entire truck mounted crane. In such units,however, although outriggers are not used, movement of the entire truckmounted crane is effected with the load and the boom centered, and notextending over the side.

Various vehicles are known which utilize tracks, and have pneumatictires, together with spring-loaded independently movable intermediate oridler wheels. In these constructions, however, there is no boom, andtherefore no overturning moment resulting from a boom positioned overthe side.

SUMMARY OF THE INVENTION

The present invention provides an aerial lift platform apparatus whichis track mounted, which has a cushioned ride for the operator in theoperator's platform, and which has improved stability againstoverturning, without the use of outriggers. The aerial lift platformapparatus comprises a chassis and a rotatable upper works mounted on thechassis for rotation through 360 degrees. The upper works includes anengine and a pump, to provide a source of hydraulic pressure for varioushydraulic operated components. A boom, preferably an extensible boom, ismounted on the upper works, preferably by a pivot so as to permitrotation of the boom in a vertical plane. An operator's platform iscarried adjacent the outer end of the boom, and is provided withcontrols for effecting movement of the entire apparatus, for rotatingthe upper works, for luffing the boom and for extending and retractingthe boom. The chassis has, on each side, front and rear wheels, and atleast one intermediate wheel. The wheels are all pneumatic tires, toprovide shock absorbing characteristics, and a track encompasses thesetires. The idlers are resiliently biased by springs, and are connectedfor conjoint movement. This provides for increased stability,particularly when the boom is over the side, while at the same timeproviding a cushioning ride for the operator in the operator's platform,which is necessarily located at a remote distance from the center of thevehicle, and is thereby subject to substantial oscillatory movement asthe vehicle is moved. The positioning of the boom over one side causessome tilting of the vehicle to that side, due in part to the added loadon the pneumatic tires, which tend to deform. This in effect raises theidler on the loaded side of the vehicle relative to a reference point onthe chassis, and the resulting conjoint movement of the idler on theopposite side tends to raise that idler from engagement with the track,and counteract the overturning movement which would be generated due tothe spring which resiliently urges the opposide-side idler intoengagement with the track.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevational view of an aerial lift platform apparatusin accordance with the present invention.

FIG. 2 is a front elevational view of the aerial lift platform apparatusas shown in FIG. 1.

FIG. 3 is a cross sectional view taken on the line 3--3 of FIG. 1.

FIG. 4 is a cross sectional view taken on the line 4--4 of FIG. 1.

FIG. 5 is a cross sectional view taken on the line 5--5 of FIG. 1, withparts removed.

FIG. 6 is a view taken on the line 6--6 of FIG. 5, and with partsrestored.

FIG. 7 is a cross sectional view taken on the line 7--7 of FIG. 6.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to the drawings, wherein like or corresponding referencenumerals are used to designate like or corresponding parts throughoutthe several views, there is shown in FIG. 1 an aerial lift platformapparatus 10 in accordance with the present invention. The apparatus 10includes an upper works 20 which is rotatable on a vertical axis, andwhich includes an engine in an engine compartment 21, the engine drivinga pump 22 for supplying fluid under pressure to various hydraulicallyoperated elements. An extensible boom 23 is provided, supported on ahorizontal pivot 24 for luffing movement. The boom 23 carries anoperator's platform 25, having a control console 26 thereon, so as toenable the operator to drive and steer the apparatus 10, and also tocause rotation of the upper works 20, extension and retraction of theboom 23 and luffing of the boom 23 about the pivot 24.

The upper works 20 is mounted on a chassis 30, which includes astructural chassis frome, and a suspension system. The suspension systemincludes end wheels 31 and 32 and intermediate wheels 33 and 34. All ofthe wheels include pneumatic tires, and a track 35 is in engagement withall of the wheels.

Referring to FIG. 2, there may be seen the two tracks 35, one on eitherside of the apparatus 10, together with the boom 23 and operator'splatform 25. There is also shown the control console 26.

In order to drive and steer the aerial lift platform apparatus 10, anoperator positions himself in the platform 25, and operates the controlsat the control console 26. In FIG. 1, the platform 25 is as close aspossible to the center of the chassis 30. When the aerial lift platformapparatus 10 is driven, therefore, even on a relatively smooth surface,there will be vibrations transmitted to the operator, and these will beamplified, due to the distance of the operator from the chassis 30.Where the aerial lift platform apparatus is driven over an uneven base,there will be imparted to the chassis 30 a pitching movement, that is, arotation about a generally horizontal axis extending transverselythrough the chassis. Since the entire apparatus 10 will thereby pitch orrotate about that axis, the platform 25 will also rotate about thataxis, and as a result the unevenness of the terrain is amplified by thedistance of the platform 25 from the pitching axis. In order to diminishdiscomfort to an operator in the platform 25, which is the onlyoperational station on the apparatus 10, the aforementioned pneumatictire suspension system is utilized, together with resilient mounting ofthe intermediate wheels 33 and 34.

Referring now to FIG. 3, there may be seen the wheel 32, including thepneumatic tire 41 mounted on a rim 42 having a disk 43. Disk 43 isbolted to a torque hub 45 of known construction, torque hub 45 beingconnected to a rotary motor 46 which is supplied with fluid from thepump 22. The motor 46 drives planetary gearing (not shown) within thetorque hub 45, to drive it. The wheel 32, including tire 41, torque hub45 and motor 46, is supported on a mount, generally designated 47. Themount 47 includes the hub mount plate 48, to which a flange of thetorque hub 45 is bolted, and also includes, in spaced relation to it, aslide plate 49. Channel 51 is secured to hub mount plate 48 and slideplate 49, as by welding, and a second channel (not shown) is positionedopposite the channel 51, so that the channels provide a space betweenthem for the motor 46. A planar structural chassis plate 37 is shown,being located in a vertical plane, and comprising a portion of thechassis 30. An L-shaped upper rail 52 and a lower L-shaped rail 53 areprovided, secured to the chassis plate 37 by screws 54 which extendthrough the rails 52 and 53 and which are threaded into threadedopenings in the plate 37. The screws 54 may be loosened to permit theslide plate 49 and thereby the wheel 32 to move horizontally, and thenthe screws 54 may be tightened so as to clamp the slide plate 49 aganstthe chassis plate 37, to secure it in a fixed position. Movement may beeffected by a suitable hydraulic motor, designated 56, and actingbetween the channel opposite channel 51 and an anchor (not shown) fixedto the chassis plate 37. This provides for effecting adjustment of thetension of the track 35 by in effect moving the wheel 32 away from thewheel 31.

In FIG. 4 there is shown the assembly of the wheel 31 to the chassis 30,there being indicated a pneumatic tire 57 mounted on a rim 58, the rimhaving a disk 59 mounted to a torque hub 61. The torque hub is supportedon a hub mount plate 62, and a rotary motor 63, supplied from the pump62, is secured to the torque hub 61 to effect driving of it. The hubmount plate 62 forms a part of a mount structure 64 which is connectedto the chassis, as to a plate similar to the chassis plate 37 shown inFIG. 3.

FIGS. 5, 6 and 7 disclose the mounting and suspension of idler wheel 33,and the corresponding idler wheel on the opposite side of the vehiclefrom that shown in FIG. 1, so that the idlers are arranged in pairs, oneon either side of the chassis, for conjoint movement.

Referring first to FIG. 7, there may be seen a portion of a structuralplate 38 forming part of the chassis. Plate 38 is shown broken away, andis provided with a first vertical edge 71, and a horizontal edge 72. Adownwardly facing channel 73 is provided, secured to the plate 38, as bywelding. The channel 73 has secured to it a bearing generally designated74, which supports the axle 75. As shown in FIG. 5, the axle 75 hasoffset ends 76 and 77, and is known as a cranked axle. Thus, the axle 75is continuous from the cranked end 76, through the central portion 78,and to the cranked end 77. A coil spring 79 encircles the centralportion 78 of axle 75, having one end connected to central portion 78and the other end connected to the bearing 74. A similar coil spring 81is also mounted on the central portion 78 of the axle 75, and isconnected to the central portion 78, and to the opposite bearing 74.

FIG. 6 discloses the channel 73 mounted in the chassis plate 38, and itwill be observed that there are symmetrical chassis plates for the twosides of the chassis. There are shown the two bearings 74, one at eitherside of the chassis and the two coil springs 79 and 81, each connectedto the axle 75 and to the adjacent bearing 74. There may also be seenhubs 82 which are journalled on the ends 76 and 77 of the continuous,cranked, axle 75, and which have joined to them disks 83 that supportrims 84 on which the pneumatic idler tires 85are mounted. As will beunderstood, the disks 83, rim 84 and tire 85 provide the elements of thewheel 33. The construction of the axle 75 provides for the above notedconjoint movement of the two idler wheels 33, which form a pair onopposite sides of the vehicle. Consequently, should the wheel 33 shownin FIG. 1 be caused to move upwardly relative to a reference point onchassis 30, the opposite wheel 33, forming the other one of the pair,will also be constrained to move upwardly, for conjoint movement. Itwill also be understood, of course, that the springs 79 and 81 provideresilient support of a portion of the weight of the chassis on theidlers 33.

In operation, a workman positions himself in the platform 25, and drivesthe aerial lift platform apparatus 10, by driving and steering, to thedesired position. During this driving movement of the aerial liftplatform apparatus 10, the pneumatic tires forming part of the wheels31, 32, 33 34 provide a cushioning effect, so as to diminish movement ofthe platform 25 which is carried at or near the end of boom 23. Inaddition, some resilient support and shock absorption is provided, bythe springs which encircle the cranked axles of the idlers 33 and 34.Thereby, a shock absorbing, cushioned ride is provided for the operatorin the platform 25.

Once the aerial lift platform apparatus 10 is in position, the upperworks 20 is rotated, and the boom 23 may, for example, be moved throughapproximately 90°, so that the boom 23 extends over one side. The boom23 may then be elevated and extended, and thus there is applied anoverturning moment to the aerial lift platform apparatus 10. Due to thepositioning of the weight of a substantial portion of the boom 23, theplatform 25 and the workman therein at a substantial distance outwardlyof the boundaries of the chassis 30, there will result a relativelygreater amount of weight applied to the track 35 and wheels 31-34 of theside of the chassis 30 over which the boom 23 extends. This will causeadded weight on the tires of each of the wheels 31-34, and these tireswill thereby be somewhat flattened. The tires on the opposite side tothat over which the boom 23 extends will bear less weight, and will notthereby be subject to a flattening force that is in addition to thenormal force, as when the upper works 20 is in the position shown inFIGS. 1 and 2. The flattening of the tires on the more heavily loadedside will result in a tilting of the structural frame of the chassis 30.Thus, there will be an overturning movement imposed by the weight andposition of the boom 23 and platform 25. Stability is enhanced, however,because the spring on each of the idler axles will not be permitted toadd to the overturning moment. The springs normally tend to raise thestructural chassis relative to the ground, and in order to do this,apply a force to the axle and through it, to the wheels and to theground, acting through the tread 35. In the present construction, theidler wheel which is less loaded, because it is on the side oppositethat over which the boom extends, is raised relative to a referencepoint on the structural frame of chassis 30, so that the spring on theaxle which is adjacent the opposite-side idler wheel does not push theopposite-side idler wheel against the track 35 and the ground andtherefore prevents the application of a force which would add to theoverturning moment created by the weight and position of boom 23 andplatform 25.

Instead, when there is a load on one side of the chassis 30, due to theover the side positioning of the boom 23, the flattening of thepneumatic tire tends to move upwardly the cranked end of axle 25: forexample, assuming that the boom is extending over the side adjacent thecranked end portion 26 as shown in FIGS. 5-7, there would be a tendencyfor the cranked end portion 76 to move in a counter-clockwise directionas seen in FIG. 7, and to thereby rotate the entire axle 75 in thecounter-clockwise direction. This would similarly raise the cranked endportion 77, which is on the side opposite to the more heavily loadedside, and there would not be a spring force, as from spring 81, whichwould tend to urge the wheel 33 carried by the cranked end portion 77against the track and ground on the opposite side. Thus, stabilityduring over the side operation is achieved, with a constructionproviding a cushioned ride so as to dampen oscillatory movements causedto the operator in platform 25 when the aerial lift platform apparatus10 moves over uneven terrain.

It will be obvious to those skilled in the art that various changes maybe made without departing from the spirit of the invention, andtherefore the invention is not limited to what is shown in the drawingsand described in the specification but only as indicated in the appendedclaims.

I claim:
 1. Aerial lift platform apparatus comprising a chassis and arotatable upper works mounted thereon,said upper works comprising aboom, said boom having an operator's platform adjacent the outer endthereof, said chassis comprising on each side first and second endwheels and at least one intermediate wheel, at least one end wheel beinga driving wheel, means mounting said end wheels on said chassis, saidwheels each including a pneumatic tire, a track on said wheels, meansfor mounting the intermediate wheels on opposite sides of the chassis asa pair for conjoint movement when the chassis is tilted to one side orthe other, and resilient means biasing said intermediate wheels awayfrom said chassis, whereby to lessen the overturning moment occurringwhen the boom extends over one side of the apparatus.
 2. The aerial liftplatform apparatus of claim 1, wherein said intermediate wheel mountingmeans comprises a transverse member extending between and connected tosaid pair of intermediate wheels.
 3. The aerial lift platform apparatusof claim 1, wherein said intermediate wheel actuating means comprises atransverse axle having cranked ends, the intermediate wheels mounted onthe cranked ends, and means on said chassis journalling said axle. 4.The aerial lift platform apparatus of claim 1, said resilient biasingmeans comprising coil spring means encircling said axle and connected tosaid axle and said chassis.
 5. The aerial lift platform apparatus ofclaim 1, said resilient biasing means comprising first and second coilsprings encircling said axle, each having one end attached to the axleand the other end connected to said chassis.
 6. The aerial lift platformapparatus of claim 1, wherein said end wheels mounting means comprisesmeans for fixedly mounting said end wheels on said chassis.
 7. Theaerial lift platform apparatus of claim 7, and means for driving two endwheels on each side of said apparatus.
 8. An aerial lift platformapparatus wherein a self propelled chassis rotatably supports an upperworks having a boom extending from it and an operator's platform carriedby the boom adjacent the free end thereof, the improvement comprisingwheels on each side of the chassis having pneumatic tires and tracksencircling the tires, there being at least three wheels on each sideincluding two fixed end wheels and an intermediate wheel, and mountingmeans for the intermediate wheels comprising means for resilientlybiasing said intermediate wheels and means for moving upwardly anintermediate wheel on one side relative to the track on that side whenthe chassis is tilted so as to raise the said one side thereof.
 9. Theaerial lift platform apparatus of claim 8 said mounting means comprisingan axle extending transversely of said chassis, means journalling saidaxle to said chassis, said axle having cranked ends, and a saidintermediate wheel journalled on each of said cranked ends.
 10. Theaerial lift platform apparatus of claim 9, and means for resilientlybiasing said axle against rotation.
 11. The aerial lift platformapparatus of claim 10, said resilient biasing means comprising coilspring means.
 12. The aerial lift platform apparatus of claim 10, saidresilient biasing means comprising coil spring means encircling saidaxle and connected to said axle and to said chassis.